Free space optical communication (FSOC) uses light propagating in free space to transmit data between two points. Since no wave guide (e.g., fiber optic cable) is used, FSOC is also known as wireless optical communication. FSOC is generally used where a physical connection through fiber optic cable is impractical, due to high costs or other considerations. Typical applications of FSOC include communication between satellites, and connections between local area networks in a campus or metropolitan area.
Free space optical transmissions through the atmosphere are susceptible to several forms of distortion caused by atmospheric turbulence. One known technique to correct for this distortion is adaptive optics, in which a deformable (adaptive) mirror in the optical path changes shape over time to cancel distortion. Part of the corrected wavefront is split off to a wavefront sensor that measures residual distortion in the wavefront. A correction signal is calculated and sent to the deformable mirror, thus forming a feedback loop. However, correction in the optical domain is costly and relatively slow.